DF (Don't frag) issues

[David Malone]

> > I wonder if we could look into the quoted IP header and extract the
> > length of the IP packet that caused the needs-frag ICMP. That would
> > stop us getting in knots when there are a few packets in flight and
> > would give us a good idea about where we need to step down from.

> This is a really clever idea indeed.  But it only works if part of
> the original packet is attached.  Broken implementations are likely
> to omit that.  But I'll implement your suggestion as well and post
> a new patch later this evening.

In the case of TCP PMTU we should be OK because we to get as far
as the TCP code I think we'll always have enough quoted packet?
Of course, in the more general case we can't always do this, but
it should help in a lot of cases.

	David.